Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.46	4.171%	$116.109	$116.11	$116.10	$116.10
Purchase #2	$86.65	13.111%	$98.0107	$98.01	$98.00	$98.00
Purchase #3	$24.46	5.339%	$25.7659	$25.77	$25.75	$25.80
Purchase #4	$101.60	9.858%	$111.6157	$111.62	$111.60	$111.60
Purchase #5	$154.56	8.360%	$167.4812	$167.48	$167.50	$167.50
Purchase #6	$97.97	9.277%	$107.0587	$107.06	$107.05	$107.10
Purchase #7	$123.32	6.264%	$131.0448	$131.04	$131.05	$131.00
7 purchase totals =	$700.02		$757.0860	$757.09	$757.05	$757.10